Evidential Theory and the Probabilistic Value of Forensic Psychology in the Legal System

The fundamental aim of legal proceedings is to reach the "material truth." Any means used to reach this truth is called "evidence." In the Turkish legal system, particularly within the framework of the Code of Criminal Procedure (CMK), the principle of "freedom of evidence" is valid. However, for a fact to be accepted as evidence, it must be obtained through legally permissible means and be consistent with reason, logic, and science. In modern judicial procedures, physical findings alone (fingerprints, DNA, weapons, etc.) are insufficient; the analysis of the mind of the "human" perpetrator of the crime also emerges as a means of proof. At this point forensic psychologyhas become one of the most strategic scientific sources of evidence for courts.

1. The Concept of Evidence in Law and the Status of Scientific Data

Evidence is a tool used to form a conscientious conviction in the judge regarding the truth or falsity of an alleged fact. According to Article 217 of the Code of Criminal Procedure, a judge can base their decision only on evidence presented and discussed in court. In law, evidence is categorized as testimonial evidence, documentary evidence, and circumstantial evidence.

Forensic psychology, within this categorization, generally finds its place through "expert opinion" or "expert report." While traditional evidence proves the external manifestation of the crime, forensic psychology concretizes the internal manifestation of the crime, that is, its reflection in the mind of the perpetrator. When courts need technical information regarding the proof (occurrence) of a fact, from forensic psychology .

2. Forensic Psychology in Determining Criminal Responsibility: Turkish Penal Code Article 32

One of the fundamental pillars of the Turkish Penal Code (TCK) is the principle of "culpability." No punishment can be imposed on a person who is not at fault. Article 32 of the TCK stipulates that no punishment shall be imposed on individuals who, due to mental illness, are unable to comprehend the legal meaning and consequences of their actions or whose ability to control their behavior is significantly diminished.

At this point, the court must obtain reports from forensic psychology and forensic psychiatry experts to determine whether the perpetrator had "the capacity for culpability." Forensic psychology , here, is not merely an "opinion," but rather "legal evidence" that directly alters the outcome of the case. Cognitive tests and behavioral analyses conducted by experts reveal the perpetrator's mental capacity at the time of the crime, providing the judge with a scientific roadmap regarding "punishability."

3. Reliability of Witness Statements and Forensic Psychology

Witness testimonies are one of the oldest, yet most misleading, types of evidence. Human memory is highly susceptible to manipulation under stress, time, fear, or external influences. Forensic psychologyacts as a filter, checking the degree to which a testimony is considered "true."

Particularly during the "witness identification" phase, forensic psychology experts evaluate the witness's psychological state at the time, the impact of environmental factors such as light and distance on perception, and phenomena such as "weapon focus." When the question of whether a statement given in court is a mental construct or a genuine memory forensic psychology techniques, the statement becomes "a means of proof beyond any doubt."

4. Victim Psychology and Statement Analysis: Particularly in Sexual Abuse Cases

In crimes where proof is difficult and often occurs between the perpetrator and the victim, forensic psychology becomes the most critical piece of evidence. In cases of child sexual abuse or domestic violence, the consistency of the victim's statement and signs of post-traumatic stress disorder forensic psychology reports.

As emphasized in the precedents set by the Supreme Court of Appeals, the victim's description of the event, their psychological reactions after the event, and the boundary between imagination and reality forensic psychology experts. These reports are the strongest evidence in forming the judge's conscientious conviction in cases where concrete evidence is lacking and "verbal contradiction" prevails.

5. Criminal Profiling and its Use as Circumstantial Evidence

Forensic psychologyhas the capacity to create "circumstantial evidence" in cases where the perpetrator has not yet been identified. Behavioral patterns (signatures) at the crime scene can create a psychological profile of the perpetrator. Although the reports of profiling experts do not directly constitute a basis for conviction, forensic psychology data provides a "logical bridge" in narrowing down the suspect's circle and integrating other collected evidence. This fills the gap between the abstract rules of law and the concrete reality of the crime.

6. Legal Status of Forensic Psychology Reports and Expert Testimony

In law, an expert witness is an "assistant to the judge." According to Article 63 of the Code of Criminal Procedure, in cases requiring expertise, specialized or technical knowledge, a decision is made to obtain the opinion and views of an expert witness. a forensic psychology expert are not binding on the court (they are discretionary evidence), if the judge decides against such a report, they must explain their decision with very strong scientific grounds.

In practice, forensic psychology reports are generally accepted as “technical evidence.” The judge makes the legal assessment himself, but forensic psychology. This forensic psychologyan integral part of legal practice.

Conclusion: Psychological Certainty for Justice

In conclusion, in the legal system, evidence refers not only to what is visible, but also to what is known and verifiable. In every area where human behavior has legal consequences, the data provided by forensic psychology is an indispensable means of proof. Forensic psychology prevents erroneous judgments by combining abstract legal norms with the complexity of the human mind. As a type of evidence , forensic psychology is the judge's most reliable compass on the path to material truth. In fulfilling the burden of proof and grounding conscientious conviction on scientific foundations , forensic psychology will continue to be one of the strongest pillars of the 21st-century legal system.